U.S. patent number 7,341,577 [Application Number 10/427,506] was granted by the patent office on 2008-03-11 for implantable drug delivery pump.
This patent grant is currently assigned to Renishaw PLC. Invention is credited to Steven Streatfield Gill.
United States Patent |
7,341,577 |
Gill |
March 11, 2008 |
Implantable drug delivery pump
Abstract
The pump includes a metering pump including a rotor, at least
two lengths of tubing against which the rotor is movable to urge
the drug therethrough, and an outlet port associated with each of
the at least two lengths of tubing. In this way, a drug may be
supplied to more than one neurological target.
Inventors: |
Gill; Steven Streatfield
(Bristol, GB) |
Assignee: |
Renishaw PLC (Gloucestershire,
GB)
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Family
ID: |
9935821 |
Appl.
No.: |
10/427,506 |
Filed: |
April 30, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20030216714 A1 |
Nov 20, 2003 |
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Foreign Application Priority Data
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Apr 30, 2002 [GB] |
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0209904.2 |
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Current U.S.
Class: |
604/288.01;
604/890.1 |
Current CPC
Class: |
A61M
5/14232 (20130101); A61M 5/14276 (20130101); A61M
2209/045 (20130101); A61M 2210/0693 (20130101) |
Current International
Class: |
A61M
31/00 (20060101); A61K 9/22 (20060101) |
Field of
Search: |
;604/151,152,154,45.01,95.02,288.01-288.04,890.1
;417/416,417,549,550 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 612 535 |
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Apr 1989 |
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EP |
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0 342 481 |
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May 1989 |
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EP |
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0 342 947 |
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May 1989 |
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EP |
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0450186 |
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Sep 2004 |
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EP |
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2 792 841 |
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Apr 2000 |
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FR |
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WO 00/66204 |
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Nov 2000 |
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WO |
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WO 01/12158 |
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Feb 2001 |
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WO |
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WO 02/11703 |
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Feb 2002 |
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WO |
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WO 02/058764 |
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Aug 2002 |
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WO |
|
Primary Examiner: Kennedy; Sharon E.
Attorney, Agent or Firm: Kohn & Associates, PLLC Kohn;
Kenneth I.
Claims
What is claimed is:
1. An implantable drug delivery pump comprising: a metering pump
including a rotor, at least two lengths of tubing against which the
rotor is moveable to urge the drug therethrough; and an outlet port
associated with each of the at least two lengths of tubing.
2. An implantable drug delivery pump according to claim 1, wherein
the metering pump includes a housing having an interior wall, and
each of the lengths of tubing is arranged between the rotor and the
interior wall of the housing whereby the rotor urges the drug
through the lengths of tubing.
3. An implantable drug delivery pump according to claim 1, wherein
the rotor includes two rotor arms.
4. An implantable drug delivery pump according to claim 1, wherein
the rotor includes three rotor arms.
5. An implantable drug delivery pump according to claim 1, wherein
the rotor includes four rotor arms.
6. An implantable drug delivery pump according to claim 1, wherein
the metering pump includes between three and six lengths of
tubing.
7. An implantable drug delivery pump according to claim 1 further
comprising a motor for moving the rotor.
8. An implantable drug delivery pump according to claim 1, wherein
the rotor carries a roller for engagement with the lengths of
tubing.
9. An implantable drug delivery pump according to claim 1 further
comprising a refill port through which a drug is insertable.
10. An implantable drug delivery pump according to claim 9, wherein
the refill port includes a seal.
11. An implantable drug delivery pump according to claim 9 further
comprising a filter unit through which the inserted drug
passes.
12. An implantable drug delivery pump according to claim 11,
wherein the filter unit is cylindrical with a central filling
well.
13. An implantable drug delivery pump according to claim 12,
wherein the filter unit includes a fluted filter.
14. An implantable drug delivery pump according to claim 11,
wherein the filter is a bacteriological filter.
15. A method of delivering a drug by implanting the apparatus of
claim 1 into a patient in need of the drug.
16. A method of providing therapy to a patient by implanting the
pump according to claim 1 into a patient in need thereof, for
providing a therapeutic to the patient.
17. A method of delivering a therapeutic agent to a plurality of
sites by implanting the pump according to claim 1 into a patient in
need thereof for the delivery of a therapeutic agent to a plurality
of delivery sites.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to UK Serial No. 0209904.2, filed
Apr. 30, 2002, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an implantable drug delivery pump,
a drug reservoir unit, and an implantable drug delivery system.
Such pumps, units, or systems may be refilled with the drug,
typically by percutaneous drug injections into reservoirs via body
tissue.
2. Background Art
Implantable drug delivery systems may be used for systemic or local
delivery of drugs. Examples of systemic drug delivery include the
regulated infusion of insulin into the body tissues for the
treatment of diabetes and the infusion of Apomorphine for the
treatment of advanced Parkinson's disease. The local delivery of
drugs or therapeutic agents has particular application to the
treatment of neurological conditions where the blood brain barrier
prevents many systemically administered drugs from reaching the
desired target, or where the delivery of drugs or therapeutic
agents to targets other than the desired target may produce
unacceptable side effects. Examples of local drug delivery into the
cerebrospinal fluid that surrounds the spinal cord and brain
include the intrathecal delivery of opioids for chronic pain
control and the intrathecal delivery of baclofen for the treatment
of spasticity. Drugs and therapeutic agents may be also delivered
directly into the brain parenchyma via a catheter whose discharge
portion lies adjacent to a predetermined target. Examples of this
type of therapy include the infusion of gamma-amino-butyric acid
agonists into an epileptic focus or pathway that will block its
transmission, the delivery of cytotoxic agents directly into a
brain tumor, and the infusion of neurotrophic agents for the
protection and repair of failing or damaged nerve cells.
Intraparenchymal delivery of neurotrophins may be used to treat a
variety of neurodegenerative disorders including Parkinson's
disease, Alzheimer's disease and Amyotrophic Lateral Sclerosis, and
may be also useful in stimulating the repair of damaged neural
tissue after injury from trauma, stroke or inflammation.
Examples of drug delivery pumps are shown, for example, in U.S.
Pat. Nos. 4,013,074 and 4,692,147, each of which describe drug
filled reservoirs located within the pump, which are positioned
within a housing that contains a gas such that when the reservoir
is filled, the gas is compressed which in turn, provides the
pressure to empty the reservoir. In particular, U.S. Pat. No.
4,692,147 describes a battery powered motor driven pump, which may
be seen in FIGS. 1 to 3 of this specification. From FIG. 1, it will
be understood that the pump 1 is implanted subcutaneously, and that
it may be refilled via a refill port 2, which may be accessed by
percutaneous drug injection. The pump 1 includes an outlet port 3
through which the drug is pumped to an outlet tube 4.
Referring to FIG. 2, it will be seen that the pump 1 includes a
pump unit 5 beneath which is located a dish 6 which defines a
reservoir. The pump unit 5 and the dish 6 are enclosed by top and
bottom parts of a housing 7, 8. The pump unit 5 includes the drug
refill port 2, batteries 9, and a roller pump 10.
FIG. 3 shows the roller pump 10 in more detail. Within the roller
pump 10 is a rotor 11 mounted for rotation within a pump housing
12. The rotor 11 includes two diametrically opposite arms, each of
which terminates in a roller 13 which engages with a length of
tubing 14 such that, as it rotates, the rollers 13 at the end of
the rotor arms crush the length of tubing to drive the fluid
through the length of tubing 14 as the rotor 11 rotates from an
inlet 15 to an outlet 16. A flexible sheet 17 overlies the length
of tubing 14, over which the roller 13 moves, the sheet 17 acting
as a shim between the length of tubing 14 and the rollers 13. An
example of a pump arranged in a similar way to that described in
U.S. Pat. No. 4,692,147 is the Synchromed EL pump (Medtronic Inc,
Minneapolis).
Passive drug reservoirs are also known where regulators control the
flow of fluid exiting a gas-pressurized drug filled reservoir. The
energy required to deliver the drug to its target is imparted to
the pump upon filling the reservoir and compressing the gas. The
regulators are either coiled lengths of fine bore tubing or etched
fluid conducting channels in a chip. Passive drug dispensers are
less reliable in delivering the desired dose than mechanical
dispensers since the dose of drug delivered by passive dispenser
depends upon the pressure in the drug filled reservoir, the
resistance set by regulator, the resistance in the pump to catheter
tubing, the resistance in the catheter, the pressure applied by the
tissue (tissue turgor) at the catheter's delivery port, as well as
the viscosity of the fluid being delivered. With passive drug
dispensers, the accuracy of drug delivery is least reliable when
the flow rates are low and the regulator needs to impart a high
resistance. In these circumstances, small changes in the viscosity
will have a significant bearing on the flow rate and the dose of
drug delivered. For the delivery of neurotrophic factors into the
brain parenchyma, low flow rates of the order of 1 10 .mu.l per
hour are desirable and because neurotrophic factors are proteins in
suspension. They will impart a higher viscosity than crystalloid
drugs and alter the flow rate accordingly. Proteins in suspension
may also have a tendency to deposit within the fine tubing or
etched channels of the passive regulator and further influence the
flow rate.
Thus, for the delivery of proteinaceous drugs and particularly the
intraparenchymal delivery of neurotrophic factors to the brain,
battery powered mechanical dispensers are preferable to passive
dispensers. For safety as well as the ability to alter the dosing
regimen as required, a pump that can be controlled by telemetry is
also desirable. Of the battery powered mechanical pumps described
in the prior art that are programmable using telemetry, all have
the drug dispenser unit containing the battery or batteries, motor,
dispensing actuator and electronics for programming housed with the
pressurized drug filled reservoir. This tends to make the pumps
bulky for subcutaneous implantation because the reservoir alone may
contain between 10 and 24 ml. The Synchromed EL pump contains a
reservoir of 16 ml, is cylindrical in shape and has a diameter of 7
cm and a height of 2.9 cm. Its size means that it is necessary to
implant such pumps subcutaneously in the anterior abdominal wall
where they are least obtrusive. Nevertheless, when implanted in
thin patients, the bulk of the pump can cause considerable
inconvenience and discomfort. If, on the other hand, the pump is
deeply placed in the subcutaneous fat of an obese patient, finding
the refill port can be also problematic. Minimizing the volume of
the reservoir of the pump has the disadvantage that the pump will
require percutaneous refilling more frequently, thereby increasing
the necessity for the patient to attend a clinic, and increasing
the risk of introducing infection.
To treat neurodegenerative disorders, brain injury or other
disorders with neurotrophins, it may be desirable to deliver them
to more than one neurological site in the central nervous system,
preferably the brain or spinal cord, most preferably the brain. For
example, Parkinson's disease may be treated by infusing
glial-derived neurotrophic factor (GDNF) delivered by one or more
catheters implanted bilaterally into each dorsal putamen.
Similarly, Alzheimer's disease may be treated by infusing nerve
growth factor delivered by one or more catheters implanted
bilaterally into each nucleus basalis.
Delivering the drug to multiple sites by implanting multiple pumps
of the types described in the prior art would be unacceptable, and
only U.S. Pat. No. 5,752,930 discloses the delivery of a drug from
a single pump to multiple sites. This teaches the fluid delivery
through a single catheter with multiple ports. Such a device will
not facilitate drug infusion bilaterally into the brain or to other
sites other than those along the axis of the implanted
catheter.
Each of the prior art documents referred to above are herein
incorporated in their entirety by this reference.
Two or more catheters could be connected to the outflow tubing from
a single pump via a single input/multiple output connector. Such an
arrangement would not guarantee an even distribution of drug to
each catheter because fluid will flow primarily down the catheter
offering the least resistance. To overcome this, the connector
would have to act as a regulator to ensure that resistance is
overcome. This will put a great demand on the pump and will
increase the stress on joints between the pump and the connector.
For very low flow rates, such as one or two .mu.l per hour, the
outflow ports in such a connector acting as a regulator will need
to be extremely small.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is
provided an implantable drug delivery pump comprising a metering
pump including a rotor, at least two lengths of tubing against
which the rotor is movable to urge the drug therethrough, and an
outlet port associated with each of the at least two lengths of
tubing. In this way, the drug can be pumped from the pump to
multiple targets in even quantities. In this specification,
references are made to the pumping and delivery of drugs, and such
references include all therapeutic agents including such substances
as proteins, cytokines, neurotrophic agents, toxins to destroy
cancerous tissue and therapeutic markers to assist in imaging
targets.
The invention allows a drug to be delivered to more than one site.
This may be for the reasons outlined above that both sides of the
brain need to be treated in conditions such as Parkinson's disease
and Alzheimer's disease, or because multiple sites of delivery
within a target volume may be necessary to optimize the
distribution of the therapeutic agent. It is generally the rule
that equal volumes of the therapeutic agent will need to be
delivered to each site. The pump of the present invention achieves
this with the advantage of being both compact and energy
efficient.
It is preferred that the metering pump includes a housing having an
interior wall, and arranged such that each of the lengths of tubing
is arranged between the rotor and the interior wall of the housing,
whereby the rotor urges the drug through the length of tubing.
It is also preferred that the rotor includes two rotor arms, and in
some circumstances it is advantageous to include three rotor arms,
or even four or more rotor arms.
The number of lengths of tubing that are included depends on the
number of targets to which it is intended to deliver the drug. In
some circumstances, it is preferred to include between three and
six lengths of tubing.
According to a preferred embodiment, the pump includes a motor for
moving the rotor, and this motor is most preferably a stepper
motor.
It is also advantageous for the rotor to carry a roller for
engagement with the length of tubing. Lower resistance and reduced
wear result from the use of the roller.
In an alternative embodiment, the lengths of tubing might be
arranged to be of different diameters such that different flow
rates are generated from different outlet ports. This will be of
particular value where the treatment of different targets require
different volumes of the drug to be delivered.
According to a second aspect of the invention, there is provided a
drug reservoir unit comprising an outer housing; a reservoir
container disposed within the outer housing and arranged to be
variable in volume; and a port through which a drug may fill or
exit from the reservoir container leading to a separately located
pump. The reference to a separately located pump in this
specification makes it clear that the reservoir unit is not an
integral part of the pump. In one embodiment, the reservoir
container is in part defined by the outer housing, and it is
preferred that in this case, the reservoir container is defined at
least in part by a bellows.
In a second embodiment, the reservoir container is defined at least
in part by a resilient bladder. The bladder is preferably
constructed from two resilient discs joined in face-to-face
relationship at their peripheries. In such a case, the outer
housing is advantageously dome-shaped. It should also be noted that
the reservoir unit could include a refill port.
According to a third aspect of the present invention, there is
provided an implantable drug delivery system comprising a drug
reservoir unit for holding a drug, a pump unit disposed remotely
from the drug reservoir unit and including a metering pump arranged
for pumping the drug from the drug reservoir unit to a delivery
zone; and a supply tube disposed between the pump unit and the drug
reservoir unit.
By locating the pump unit and the drug reservoir separately, the
pump unit will be more compact, and may allow a surgeon to implant
it in a range of alternative locations where it is comfortable and
access to the refill port is improved. Also, by locating the drug
reservoir unit separately, the unit may be arranged to hold a
greater volume of the drug, thereby reducing the number of clinic
visits for percutaneous refilling, and also reducing the risk of
introducing infection. A limitation on the size of the reservoir is
the stability of the drug because there is no valve in the
reservoir being of greater capacity than the total volume of a drug
that will be delivered at the prescribed rate before the drug
begins to degrade.
The reservoir should be preferably located subcutaneously over the
abdominal wall and most preferably within the rectus sheath,
overlying the rectus muscles of the anterior abdominal wall because
this will tend to reduce its prominence.
For drug delivery to the brain, it is preferable to position the
pump close to the head. This minimizes the length over which the
pump outflow tubing needs to be tunnelled subcutaneously, reduces
the dead space in the tubing and also reduces the resistance to the
flow of fluid, thereby improving energy efficiency for pump.
According to preferred embodiments, an outlet tube leads from the
pump unit to the delivery zone. It is preferred that a plurality of
outlet tubes lead to a plurality of delivery zones, so that
treatment is optimized.
It is also preferred that the pump unit further includes a drug
refill port through which the reservoir is filled. This is
preferred because the pump unit may be unobtrusively implanted in
the subclavicular region while the bulkier drug reservoir may be
implanted in the abdominal wall. Whereas the anterior abdominal
wall may contain considerable subcutaneous fatty tissue, the
subclavicular region has comparatively little subcutaneous fat and
so if the drug port is housed with the drug dispenser, it should be
relatively easy to palpate percutaneously.
It is least intrusive, and therefore preferred, if the drug refill
port is arranged to fill the reservoir via the supply tube. Filling
will result in the flow of the drug through the supply tube in the
opposite direction to the supply of the drug to the pump unit
during drug delivery.
It is preferred that the system further comprise one or more
neurosurgical catheters for delivering the drug to delivery
zones.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the present invention are readily appreciated
as the same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings wherein:
FIG. 1 is a prospective view of a prior art device;
FIG. 2 is an exploded view of the prior art device shown in FIG. 1;
and
FIG. 3 is a cross-sectional plan view of the prior art device shown
in FIG. 1.
FIG. 4 is a schematic view showing an implantable drug delivery
system according to the present invention;
FIG. 5 is a rear view of a pump unit according to the present
invention, with part of the casing removed to reveal the interior
of the unit;
FIG. 6 is a front view of the pump unit shown in FIG. 5, but with
the casing in place;
FIG. 7 is an underside view of the pump unit of FIGS. 5 and 6;
FIG. 8 is a partially exploded view of the pump unit of FIGS. 5 to
7;
FIG. 9 is a more fully exploded view of the pump unit shown in
FIGS. 5 to 8;
FIG. 10 is a sectional view of a filter unit of the pump unit
viewed from the front;
FIG. 11 is a sectional view of part of the filter unit as viewed
from below;
FIG. 12 is an exploded view of a drug reservoir unit;
FIG. 13 is a perspective view of the drug reservoir unit shown in
FIG. 12;
FIG. 14 is a sectional view of the drug reservoir shown in FIGS. 12
and 13;
FIG. 15 is an exploded view of an alternative form of drug
reservoir according to the present invention;
FIG. 16 is a perspective view of the reservoir of FIG. 15; and
FIG. 17 is a sectional view through the reservoir unit shown in
FIGS. 15 and 16.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 4 is a schematic view showing an implantable drug delivery
system. A reservoir unit 21 is shown implanted subcutaneously over
the anterior abdominal wall of a patient, and preferably within the
rectus sheath anterior to the rectus muscle. The reservoir unit 21
has the purpose of holding a volume of a drug for infusion, and
since the unit 21 is quite bulky in order to retain as much drug as
possible, such a location is very suitable. Leading from the
reservoir unit 21 is a supply tube 22, which leads to a pump unit
23. The supply tube 22 is tunnelled subcutaneously between the
reservoir unit 21 and the pump unit 23. The pump unit 23 is
subcutaneously implanted in the subclavicular region. Implantation
at this location is possible since the pump unit 23 is compact,
made possible by the remote location of the reservoir unit 21. This
location for the pump unit 23 is particularly advantageous since it
should not prove to be inconvenient or uncomfortable to the
patient, and yet it is close enough to the surface of the body that
percutaneous refilling is relatively easy. It will be seen from
FIG. 4 that the pump unit 23 includes a refill port 24 on its front
surface through which it is easy to palpate. The pump unit 23
includes one or more outlet ports 25 from which the drug is pumped
into one or more outlet tubes. The outlet tubes 26 lead to
intraparenchymal catheters 27 which are implanted in the brain of
the patient.
Intraparenchymal catheters are known in the field of neurosurgery
for infusing drugs to particular parts of the brain. The catheters
are rigid tubes, which are inserted stereotactically and secured to
the skull with their distal ends in the vicinity of targets to be
treated within the brain. The intraparenchymal catheters 27 are
connected to the outlet tubes 26 which are tunnelled subcutaneously
through the scalp and neck.
It will be understood that, while there are often major advantages
to delivering a drug to more than one target within the brain, the
advantages of locating the reservoir unit 21 and the pump unit 23
separately can be also extremely advantageous where a drug is
delivered to just one target.
Once the drug delivery system has been installed in the body of the
patient, the reservoir unit 21 may be filled by inserting a
hypodermic needle through the skin of the patient through the
refill port 24. The drug can be then inserted into the pump unit 23
where it is directed through the supply tube 22 to the reservoir
unit 21. The reservoir unit 21 is arranged such that the drug
contained therein is held there under a pressure, which urges the
drug upwards to the pump unit 23. This way, the pump unit 23 merely
pumps the drug from the pump unit 23 to the target, and does not
have to draw the drug from the reservoir unit 21. This will clearly
reduce the power consumed by the pump unit 23 and assist in
preserving battery life. The speed and operation of the pump unit
23 can be preset, although it is preferable for it to be
telemetrically controlled from outside of the patient's body.
During pumping, the drug is pumped at a steady rate from the outlet
ports 25, via the outlet tubes 26 to the neurosurgical catheters
27, where the drug is released at the target to be treated. In
certain applications, the flow rate of the drug being administered
may be of the order of one to ten .mu.l per hour.
Referring to FIGS. 5 to 9, the pump unit 23 is shown including the
outlet ports 25 in the form of connectors for connecting to lengths
of tubing. The pump unit 23 also includes an inlet port 28 in the
form of a connector, whereby the supply tube 22 may be connected.
Within the pump unit 23 is located a battery 29, a roller pump 30,
a refill port/filter unit 31 and two electronics modules 32. From
FIG. 5 it will be seen that the roller pump 30 includes a housing
33 having a curved interior wall, a rotor 34 rotatable within the
housing and arranged with two diametrically opposite rotor arms
each of which ends in a roller 35. A dual length of tubing 36 is
disposed against the curved interior wall of the housing 33 such
that the rollers 35 crush the tubing 36 against the interior wall
of the housing 33. When the rotor 34 is rotated, the rollers 35
roll over the dual length of tubing 36 so as to urge any fluid
within the tubing therethrough. It is this, which generates the
pumping of fluids through the drug delivery system. Although not
shown in the drawings, a shim or flexible sheet is disposed over
the tubing 36 such that the rollers 35 do not bear directly on the
tubing 36, but on the shim, thereby reducing wear on the tubing 36.
An example of a shim is shown in FIG. 3. The rotor 34 is rotated by
a stepper motor (not shown), although other suitable motors could
be used. It will be understood that a dual length of tubing 36 is
one where two tubes extend side by side, as is seen in FIG. 9.
It will be appreciated that the inlet port 28 leads fluid from the
reservoir unit 21 via the supply tube 22 into the roller pump 30.
Since the length of tubing 36 within the roller pump 30 is dualled,
this means that one inlet line can be converted to two outlet
lines. In this regard, it will be seen that there are two outlet
ports 25, each connected to one of the lengths of tubing 36 passing
through the roller pump 30. In FIG. 5, only one of the lengths of
tubing 36 through the roller pump 30 can be seen since the length
of tubing will be stacked axially with respect to the axis of
rotation of the rotor, but the tubing 36 is best seen in FIG. 9. Of
course, the use of two lengths of tubing 36 means that the same
volume of a drug will be delivered to two different targets. Of
course, more lengths of tubing may be incorporated here, each of
which is acted upon by the roller 35 of the rotor 34 in order to
pump the drug to each site to which it is desired to pump the drug.
In fact, if different sites required different volume of the drug
to be delivered to them, the length of tubing 36 passing through
the roller pump 30 can be arranged to have different internal
diameters, thereby allowing pumping at different rates through
different lengths of tubing. Further details of the refill port 24
and the filler unit will be described later in the
specification.
FIG. 9 shows a more exploded view of the pump unit. It will be seen
that in alignment with the refill port 24 is a filter element 37
and a silicone rubber seal 38. The seal 38 closes the port 24 so
that nothing can pass either way through the port 24 unless it is
inserted using a hypodermic needle from outside. The seal is able
to form a seal around the hypodermic needle during filling of the
system, and once the needle has been removed, the hole that the
needle made will be securely sealed closed again in order to
prevent foreign bodies from entering the system, and to prevent the
drug from escaping from within the system.
During filling, the tip of the hypodermic needle is located within
the central well of the filter element 37, and during filling, the
drug must pass through a cylindrical bacterial filter 39 that is
arranged around the outside of the filter element, and is, in this
case, fluted. The filter element is arranged like a reel.
During filling, the drug from the hypodermic needle is forced
through the fluted bacteriological filter 39 and is directed down
through the supply tube 22 into the reservoir unit 21. The filter
prevents any particulate matter within the drug that is inserted
from being passed into the rest of the system, the particulate
matter being retained within the filter element 37. The particulate
matter can be, for example, fragments of skin, hair or bacteria.
Implantable pumps require a filter to screen out the particulate
matter. Fine filters provide resistance to the flow of fluid, and
to reduce this, the surface area is maximized. Whereas it is known
to use large discs of porous material through which the fluid is
passed, this necessarily occupies a relatively large space where
space is at a premium. The filter in the present invention is very
compact and is positioned at the refill port rather than between
the reservoir and the pump, and so prevents any particulate matter
from entering the reservoir in the first place. When the system is
emptied by aspirating through the refill port, particulate matter
may be flushed out of the filter, and so help clean it. The
resistance offered by the filter in the present invention is
overcome when fluid is injected into the refill port and avoids the
increase in demand on the pressurized reservoir to overcome the
filter resistance, which is inherent in the teaching of the prior
art. The increased resistance in the prior art may contribute to a
fall off in the pressure of fluid delivery to the pump as the
reservoir becomes depleted, and may contribute to inaccuracies in
drug delivery. The bacterial filter is intended to have a four
micron mesh size.
The pump unit is closed by a lower casing 30A and an upper casing
30B, each of which is made of titanium. The various components
shown in FIG. 9 are spot welded to pins located within the upper
casing 30B. The refill port 24 is pressed onto the interior surface
of the upper casing 30B prior to laser welding the two halves of
the casing together.
In the upper casing 30B, an alarm unit 41 can be seen which might
be used to draw the patient's attention to some potential problem
with the system.
FIGS. 10 and 11 show the filter unit 31 in more detail with the
filter element 37 mounted in place. The seal 38 can clearly be seen
in FIG. 11, through which the drug is injected. It can also be seen
that the inlet port 28 extends from the filter unit 31 so that the
drug, on its way to the patient from the reservoir unit 21, passes
through the filter unit 31 on its way to the roller pump 30.
FIGS. 12, 13, and 14 show a first design of a reservoir unit 47.
The reservoir unit includes a top casing 42, which is cylindrical
in shape, closed at one end, a bottom plate arranged to close the
open top of the top casing 42, and bellows 44 located within the
top casing and bottom plate. The bottom plate 43 includes an
inlet/outlet port 45 through which the drug passes to fill the
reservoir unit, and to lead via the supply tube 22 to the pump unit
23. The bottom plate 43 and bellows 44 define a sealed fluid
reservoir. The space outside of the fluid reservoir, but within the
housing, is also sealed and contains a small amount of fluorocarbon
fluid or other volatile fluid that will provide positive pressure
against the bellows sufficient to force the liquid out of the
reservoir via the inlet/outlet port 45 towards the pump 23. The
reservoir unit may be of any suitable size depending on the
requirements of the individual patient. Typical volumes of the
reservoir may be 10 ml, 20 ml or 30 ml. The reservoir would
preferably have a low profile with rounded edges in order to be as
unobtrusive as possible to the patient. The top case in 42 and the
bottom plate 43 are titanium.
FIGS. 15, 16, and 17 show a second embodiment of reservoir. This
reservoir includes a domed lower casing 51, a domed upper casing 52
and a resilient bladder 53 disposed therebetween. The bladder 53 is
constructed from two polyurethane discs placed face-to-face and
sealed around their peripheries. The bladder 53 includes an
inlet/outlet port 54 for connection to the supply tube 22 leading
to the pump unit 23. The space outside of the bladder, but within
the casing 51, 52, is a partial vacuum. The bladder 53 has
sufficient resilience to expel any drug, and the partial vacuum
ensures constant outflow pressure.
The materials used for various components of the system must be
those, which are most tolerable to the body of the patient in order
to reduce the risk of rejection systems. It is for this reason that
the casings of the pump unit and the reservoir unit are constructed
from titanium, although other materials might be also suitable.
The inlet port 28 and the outlet ports 25 to the pump unit 23, and
the inlet/outlet port 45, 54 of the reservoir unit are, in this
embodiment, in the form of a nipple over which the various tubes
must be forced and subsequently compressed by tightening a
ligature, a crimped ring, a deformed washer that is compressed by a
threaded encircling nut, or by other suitable means.
It will be appreciated that the modular nature of the drug delivery
system means that, if the pump unit 23 were to fail, or the battery
to run down, the pump unit 23 may be surgically replaced while
leaving the reservoir unit 21 and the neurosurgical catheters 27 in
place. The new pump unit is merely reconnected to the various
tubes. Also, the modular arrangement allows a pump to be used in a
system with a variety of different types and sizes of reservoir. A
smaller reservoir is suitable where very low flow rates are to be
used, and where the drug being used has a short storage life. Also,
if the reservoir needs to be replaced, this can be done without
disturbing the rest of the system. Such a modular arrangement would
be just as suitable if there were only one outlet port 25 leading
from the pump unit 23.
Certain drugs, which are used for delivery to parts of the body are
inherently toxic, or have serious side effects. Therefore, such
drugs are normally delivered in a composition including a
neutralizing substance. However, the storage life of the
composition tends to be much shorter than the storage life of the
drug on its own. As a result, in the present invention, the drug
can be stored in one reservoir, and the neutralizing substance in
another, and outlets from each of the reservoirs can lead to inlets
to the pump. The pump will then pump the two substances in the
appropriate proportions, such that after pumping, the two
substances are allowed to mix and are fed through the system to the
catheter for delivery. It will be appreciated that the mixing
proportions will be controlled by the sizes of the respective
length of tubing passing through the pump.
As explained above, although the present embodiment includes two
outlet ports 25, the roller pump 30 can be arranged such that the
rotor passes over more lengths of tube in order to pump the drug to
more targets within the body such as the spinal cord.
The rotor 34 in the present embodiment includes two arms, each of
which terminates in a roller. However, it is possible to increase
the number of rollers above two.
Since the pump unit may be controlled by non-invasive telemetry,
the rate of rotation of the rotor can be adjusted to adjust the
rate of which the drug is delivered.
Throughout this application, various publications, including United
States patents, are referenced by author and year and patents by
number. Full citations for the publications are listed below. The
disclosures of these publications and patents in their entireties
are hereby incorporated by reference into this application in order
to more fully describe the state of the art to which this invention
pertains.
The invention has been described in an illustrative manner, and it
is to be understood that the terminology, which has been used is
intended to be in the nature of words of description rather than of
limitation.
Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is,
therefore, to be understood that within the scope of the appended
claims, the invention can be practiced otherwise than as
specifically described.
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